Barry Sanders | University of Calgary (original) (raw)

Papers by Barry Sanders

We investigate a method for generating nonlinear phase shifts on superpositions of photon number ... more We investigate a method for generating nonlinear phase shifts on superpositions of photon number states. The light is stored in a Bose-Einstein condensate via electromagnetically induced transparency memory techniques. The atomic collisions are exploited to generate a nonlinear phase shift of the stored state. The stored light is then revived with the nonlinear phase shift imprinted upon it. We show that this method can be used as a nonlinear-sign gate in the regime where the Thomas-Fermi and mean-field approximations are valid. We test these approximations using realistic parameters and find that these approximations pass the standard tests for validity in a single-component condensate. However, for the two-component condensates considered here, we find that these conditions are insufficiently strict. We find a stronger set of conditions and show for the same set of parameters that the approximations are invalid.

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Physical Review A, 1992

Erratum: Entangled coherent states [Phys. Rev. A 45, 6811 (1992)]. Barry C. Sanders. URL: http://... more Erratum: Entangled coherent states [Phys. Rev. A 45, 6811 (1992)]. Barry C. Sanders. URL: http://link.aps.org/doi/10.1103/PhysRevA.46.2966 DOI: 10.1103/PhysRevA. 46.2966 PACS: 42.50.Wm, 42.50.Dv, 03.65.Bz, 99.10.+g. ...

Proceedings of the National Academy of Sciences, 2010

Cellular energy production depends on electron transfer (ET) between proteins. In this theoretica... more Cellular energy production depends on electron transfer (ET) between proteins. In this theoretical study, we investigate the impact of structural and conformational variations on the electronic coupling between the redox proteins methylamine dehydrogenase and amicyanin from Paracoccus denitrificans. We used molecular dynamics simulations to generate configurations over a duration of 40 ns (sampled at 100-fs intervals) in conjunction with an ET pathway analysis to estimate the ET coupling strength of each configuration. In the wild-type complex, we find that the most frequently occurring molecular configurations afford superior electronic coupling due to the consistent presence of a water molecule hydrogen-bonded between the donor and acceptor sites. We attribute the persistence of this water bridge to a "molecular breakwater" composed of several hydrophobic residues surrounding the acceptor site. The breakwater supports the function of nearby solvent-organizing residues by limiting the exchange of water molecules between the sterically constrained ET region and the more turbulent surrounding bulk. When the breakwater is affected by a mutation, bulk solvent molecules disrupt the water bridge, resulting in reduced electronic coupling that is consistent with recent experimental findings. Our analysis suggests that, in addition to enabling the association and docking of the proteins, surface residues stabilize and control interprotein solvent dynamics in a concerted way. respiratory chain | Marcus theory | pathway model | dynamic docking | blue copper proteins

Journal of the American Chemical Society, 2011

Transition-state theory (TST) is a widely accepted paradigm for rationalizing the kinetics of che... more Transition-state theory (TST) is a widely accepted paradigm for rationalizing the kinetics of chemical reactions involving one potential energy surface (PES). Multiple PES reaction rate constants can also be estimated within semiclassical approaches provided the hopping probability between the quantum states is taken into account when determining the transmission coefficient. In the Marcus theory of electron transfer, this hopping probability was historically calculated with models such as Landau-Zener theory. Although the hopping probability is intimately related to the question of the transition from the fully quantum to the semiclassical description, this issue is not adequately handled in physicochemical models commonly in use. In particular, quantum nuclear effects such as decoherence or dephasing are not present in the rate constant expressions. Retaining the convenient semiclassical picture, we include these effects through the introduction of a phenomenological quantum decoherence function. A simple modification to the usual TST rate constant expression is proposed: in addition to the electronic coupling, a characteristic decoherence time τ(dec) now also appears as a key parameter of the rate constant. This new parameter captures the idea that molecular systems, although intrinsically obeying quantum mechanical laws, behave semiclassically after a finite but nonzero amount of time (τ(dec)). This new degree of freedom allows a fresh look at the underlying physics of chemical reactions involving more than one quantum state. The ability of the proposed formula to describe the main physical lines of the phenomenon is confirmed by comparison with results obtained from density functional theory molecular dynamics simulations for a triplet to singlet transition within a copper dioxygen adduct relevant to the question of dioxygen activation by copper monooxygenases.

Physical Review A, 2014

We develop a complete resource theory of charge-parity-time (CPT) inversion symmetry for both mas... more We develop a complete resource theory of charge-parity-time (CPT) inversion symmetry for both massive and massless relativistic particles of arbitrary spin. We show that a unitary representation of CPT can be consistently constructed for all spins and develop the resource theory associated with CPT super-selection, thereby identifying and quantifying the resources required to lift the super-selection rule.

Physical Chemistry Chemical Physics, 2012

Over recent decades, quantum effects such as coherent electronic energy transfers, electron and h... more Over recent decades, quantum effects such as coherent electronic energy transfers, electron and hydrogen tunneling have been uncovered in biological processes. In this Perspective, we highlight some of the main conceptual and methodological tools employed in the field to investigate electron tunneling in proteins, with a particular emphasis on the methodologies we are currently developing. In particular, we describe our recent contributions to the development of a mixed quantum-classical framework aimed at describing physical systems lying at the border between the quantum and semi-classical worlds. We present original results obtained by combining our approach with constrained Density Functional Theory calculations. Moving to coarser levels of description, we summarize our latest findings on electron transfer between two redox proteins, thereby showing the stabilization of inter-protein, water-mediated, electron-transfer pathways.

Electronics Letters, 2006

Abstract Experimental waveguides, bends and power dividers in the woodpile electromagnetic bandga... more Abstract Experimental waveguides, bends and power dividers in the woodpile electromagnetic bandgap (EBG) material at Ku-band are demonstrated. Prototypes are fabricated from alumina, and use an efficient waveguide transition to enable high quality ...

A resonator antenna made from a complex artificial surface and a metallic ground plane is describ... more A resonator antenna made from a complex artificial surface and a metallic ground plane is described. The complex surface is realized using a woodpile electromagnetic bandgap (EBG) material, which is shown to have a frequency dependent reflection plane location. A highly directive radiation pattern is created due to the angle-dependent attenuation of the resonator antenna coupling to free space. The antenna has the advantages of low height, low loss, and low sidelobes. It is shown that the directivity can be varied over a fixed range by changing the aperture size of the device, with the maximum directivity determined by both the feed element and EBG material properties. The complete bandgap for the woodpile EBG material is confirmed from a band diagram, and its properties as a complex surface are investigated through transmission calculation and measurement. The design of the antenna is described, and two means of exciting the resonator, a microstrip patch and a double slot, are investigated. Theoretical results for these two antennas are calculated the using finite-difference time-domain and are shown to be in good agreement with measured results.

Physica E: Low-dimensional Systems and Nanostructures, 2001

Based on the global coherent tunneling model, we present a self-consistent calculation and show t... more Based on the global coherent tunneling model, we present a self-consistent calculation and show that structural asymmetry of double barrier resonant tunneling structures (DBRTSs) signiÿcantly modiÿes the current-voltage characteristics compared to the symmetric structures. Within the framework of the dielectric continuum model, we further investigate the phonon-assisted tunneling (PAT) current in symmetric and asymmetric DBRTSs. Both the interface modes and the conÿned bulk-like longitudinal-optical phonons are considered. The results indicate that the four higher-frequency interface phonon modes (especially the one which has the largest electron-phonon interaction at either interface of the emitter barrier) dominate the PAT processes. We show that a suitably designed asymmetric structure can produce much larger peak current and absolute value of the negative di erential conductivity than its commonly used symmetric counterpart. of its potential applications in electronic devices and also due to its value in exploring fundamental phenomena [2], including tests of electron-phonon coupling theories . Despite extensive studies of the DBRTS, challenging problems remain with respect to practical applications and also for modeling the characteristics of the DBRTS [2]. Our objective here is to fully analyze the space-charge e ects and the 1386-9477/01/$ -see front matter c 2001 Elsevier Science B.V. All rights reserved. PII: S 1 3 8 6 -9 4 7 7 ( 0 1 ) 0 0 1 4 7 -3

Australian Journal of Physics, 2013

Based on the dielectric continuum model, we calculated the phonon assisted tunneling (PAT) curren... more Based on the dielectric continuum model, we calculated the phonon assisted tunneling (PAT) current of general double barrier resoant tunneling structures (DBRTSs) including both symmetric and asymmetric ones. The results indicate that the four higher frequency interface phonon modes (especially the one which peaks at either interface of the emitter barrier) dominate the PAT processes, which increase the valley current and decrease the PVR of DBRTSs. We show that an asymmetric structure can lead to improved performance. 73.40.Gk, 73.50.Bk

CLEO: 2013, 2013

ABSTRACT We develop a theory for multi-channel passive optical interferometery with one or zero p... more ABSTRACT We develop a theory for multi-channel passive optical interferometery with one or zero photon entering each input port, and we show that the output photon coincidences yield information about immanants of the interferometer transformation matrix.

The N00N state, which was introduced as a resource for quantum-enhanced metrology, is in fact a s... more The N00N state, which was introduced as a resource for quantum-enhanced metrology, is in fact a special case of a superposition of two SU(2) coherent states. We show here explicitly the derivation of the N00N state from the superposition state. This derivation makes clear the connection between these seemingly disparate states as well as shows how the N00N state can be generalized to a superposition of SU(2) coherent states.

Microwave and Optical Technology Letters, Aug 24, 2005

analysis of the structure with the hybrid method at f ϭ 9 GHz are shown in . Specifically, the ra... more analysis of the structure with the hybrid method at f ϭ 9 GHz are shown in . Specifically, the radiation patterns in the x-z and y-z planes are plotted in Figures 6(a) and 6(b), respectively. For this analysis, the waveguide is inside an FEM domain and the conducting planes are taken into account by means of PO and PO ϩ PTD (FEM ϩ PO and FEM ϩ PO/PTD labels in , respectively). Obviously, mutual interactions between the conducting planes have been computed using the appropriate HFT (PO or PO ϩ PTD). Agreement between the measurements and the results obtained using the hybrid technique is very good.

For Doppler-broadened media operating under double-double electromagnetically induced transparenc... more For Doppler-broadened media operating under double-double electromagnetically induced transparency (EIT) conditions, we devise a scheme to control and reduce the probe-field group velocity at the center of the second transparency window. We derive numerical and approximate analytical solutions for the width of EIT windows and for the group velocities of the probe field at the two distinct transparency windows, and we show that the group velocities of the probe field can be lowered by judiciously choosing the physical parameters of the system. Our modeling enables us to identify three signal-field strength regimes (with a signal-field strength always higher than the probe-field strength), quantified by the Rabi frequency, for slowing the probe field. These three regimes correspond to a weak signal field, with the probe-field group velocity and transparency window width both smaller for the second window compared to the first window, a medium-strength signal field, with a probe-field group velocity smaller in the second window than in the first window but with larger transparency-window width for the second window, and the strong signal field, with both group velocity and transparency window width larger for the second window. Our scheme exploits the fact that the second transparency window is sensitive to a temperature-controlled signal-field nonlinearity, whereas the first transparency window is insensitive to this nonlinearity.

Charge qubits are promising quantum logical elements for performing quantum computation or as int... more Charge qubits are promising quantum logical elements for performing quantum computation or as intermediate states to prepare and read other qubit realizations such as spin or flux. Instead of idealizing the charge qubits at the outset and using standard quantum circuit theory, we use the extended Hubbard model as a first-principles model of charge qubit dynamics and model idealized proposals for charge-qubit circuits using this second-quantized description with short- and medium-range interactions. In particular we study how one- and two-qubit gates would perform for realistic systems, and we apply our theory to teleportation of a single charge qubit in a three-qubit system. We also discuss how to incorporate phonon noise into the model.

J Phys a Math Theor, 2010

We introduce a class of bipartite entanglement measures based on Rényi-α entropy, namely Rényi-α ... more We introduce a class of bipartite entanglement measures based on Rényi-α entropy, namely Rényi-α entanglement with an analytic formula in two-qubit systems for α >= 1. We also show that multi-qubit entanglement has a monogamy inequality in terms of Rényi-α entanglement for all α >= 2.

IEEE Antennas and Propagation Society International Symposium. Digest. Held in conjunction with: USNC/CNC/URSI North American Radio Sci. Meeting (Cat. No.03CH37450), 2003

Abstract We demonstrate two antennas that use two different electromagnetic bandgap materials. Th... more Abstract We demonstrate two antennas that use two different electromagnetic bandgap materials. The first is a thin, high gain resonator antenna formed from a three-dimensional electromagnetic bandgap material and a metallic ground plane. The second structure is a ...

By generalizing a quantum walk to include measurement of the path taken by the quantum walker, we... more By generalizing a quantum walk to include measurement of the path taken by the quantum walker, we show that quantum walks interpolate between a fully coherent quantum dynamics and a classical random walk, depending on how strongly the walker's coin state is measured; i.e., the quantum walk exhibits the quintessentially quantum property of complementarity.